Heavy metal salts or complexes of organic acids have commonly been prepared by reacting a heavy metal chloride or sulfate with an alkali metal salt of the acid. In these reactions, the usual by-product salts such as NaCl, Na.sub.2 SO.sub.4, KCl, LiCl and K.sub.2 SO.sub.4 are highly soluble in aqueous media. In the formation of metal complexes, it has been proposed to remove such by-product salts by a technique of extraction as, for example, disclosed in U.S. Pat. No. 4,055,655. However, such extraction techniques become difficult or even prohibitively expensive. The need for synthesizing second salt-free aqueous and solid preparations of heavy metal salts or chelates is high-lighted by a brief consideration of the end uses of such salts or chelates. For instance, in the case of employing such complexes as antimicrobial agents, the mentioned common second salts are all potentially irritating to normal skin, and markedly irritating to denuded or injured tissue. In industrial applications, such common salts are found to be corrosive to the metals in machinery and work pieces. Thus, a method for the production of metal salts or complexes of organic acids which are second salt-free would be highly desirable, particularly when such complexes are used in any application in which such salts may be potentially harmful or unwanted.
The classic heavy metal donors which are employed in prior art techniques are heavy metal chlorides or sulfates. These classic salts provide lower percentages by weight of the heavy metal ion in the salt in comparison, for example, to the corresponding heavy metal carbonates or hydroxides. For instance, the percent of copper in CuCl.sub.2 .multidot.2H.sub.2 O and CuSO.sub.4 .multidot.5H.sub.2 O is approximately 37 and 25%, respectively. In contrast, the percent of copper in copper hydroxide is approximately 80%. However, the copper hydroxide as a possible form of heavy metal donor, which potentially provides a more efficient source of heavy metal ion, is relatively inert.